Is graphene a stable platform for photocatalysis? Mineralization of reduced graphene oxide with UV-irradiated TiO₂ nanoparticles

The recent thrust in utilizing reduced graphene oxide (RGO) as a support for nanostructured catalyst particles has led to the claims of improved efficiency in solar cells, fuel cells, and photocatalytic degradation of pollutants. Specifically, the robust TiO₂ system is often coupled with RGO to improve charge separation and facilitate redox reactions. Here, we probe the stability of RGO in the presence of UV-excited TiO₂ in aqueous media and establish its reactivity toward OH^̇ radicals, a primary oxidant generated at the TiO₂ surface. By probing changes in absorption, morphology, and total organic carbon content (TOC), we conclusively demonstrate the vulnerability of RGO toward OH^̇ attack and raise the concern of its use in many applications where OH^̇ are likely to be formed. On the other hand, the OH^̇ radical-mediated mineralization could also enable new approaches in tackling environmental remediation of nanocarbons such as RGO, carbon nanotubes, and fullerenes.